<!DOCTYPE html>
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<head>
    <meta charset="UTF-8">
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    <title>Document</title>
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<body>
    
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<script>
var i=0;
var j=0;
 var borderWidth =1;
var tableWidth=400;
var tableHeight=400;
var str = "hello";
var str1 = "world";
var str2 = 1;
var str3 = "hello" + str2 + "world";
document.write("<table border='"+borderWidth+"' height='"+tableHeight+"'width='"+tableWidth+"''>");
while(i<4){
    document.write("<tr>");
        j=0;//如果 不加，那么第一次循环后j就等于了4，第二次循环就不会执行了
    while(j<4){
        document.write("<td>");
        document.write("</td>");
        j++;
    }
 docunment.write("</tr>");
 i++;
}
docunment.write("</table>");


</script>
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